In general, a probe for use in a scanning tunneling microscope is manufactured by an electrolytic polishing method using tungsten. As shown in FIG. 4, tungsten wire 10 and platinum wire 11 were dipped and held in a sodium nitrite solution (20 g/100 ml H.sub.2 O), and 30 V from a voltage generator 12 was applied between the tungsten wire and platinum wire with the tungsten wire supplying a positive potential. About 1 mm of the tungsten wire was inserted vertically in the above-mentioned solution. The voltage continued to be applied until bubbles did not rise from the tungsten wire and flashing stopped. After taking out the tungsten wire from the sodium nitrite solution, the tungsten wire was washed with pure water for five minutes, then with ethanol for five minutes. As a result, the sharp probe having a tip was manufactured.
According to a probe for use in a scanning tunneling microscope which was manufactured by a conventional method, it was effective to examine an image of atom on a plain surface of a substrate having at most 1 nm of roughness, such as graphite and silicon. However, there is a problem in examining a macromolecule, i.e., a molecule of protein, which is formed on a surface of a solid state.
Consequently, the details of the problem abovementioned are explained using figures as follows.
In FIG. 5, 20 designates a probe, 21 designates a sample substrate, 22 designates a substrate, 23 designates a tunneling current. As shown in FIG. 5, when a probe 20 is sharpened ideally, a tunneling current occurs only through a tip of a probe. However, in general, a probe is not sharpened like a probe 20. As shown in FIG. 6, a tunneling current 23 occurs through a side part of a probe 24. A scanning tunneling microscope is manufactured for analyzing the shape of a sample substrate providing that the tunneling current 23 occurs between the tip of a probe 24 and the sample substrate 21. As shown in FIG. 6, an accurate image of molecules could not be obtained.
This invention aims to provide a probe for use in a scanning tunneling microscope. The probe has a sharp tip which can measure a macromolecule, i.e., a protein molecule. The invention also provides a method of manufacturing the probe for use in a scanning tunneling microscope.